粤东北某铀矿集中区地下水中氡浓度调查研究

Investigation of radon concentration in groundwater in a uranium concentration area in northeast Guangdong

粤东北某铀矿集中区矿产资源丰富,是广东省重要的核原料基地之一。基于区内地下水中氡浓度的调查结果,分析不同区域地质环境、水源类型等因素,解释区内各地下水中氡浓度差异的原因,评估区内地下水中氡对当地辐射环境和居民的影响,指明地下水使用过程中应注意的问题,提出加强辐射环境保护的措施及建议。结果表明:(1)研究区铀矿的富集会造成当地天然放射性本底的偏高,铀矿探采过程中产生的废石、粉尘和废水中含有^(238)U、^(232)Th、^(226)Ra等放射性核素,在雨水及径流的冲刷渗透作用下都可能对当地造成放射性污染,特别是氡气可以在岩矿缝隙、表层土壤、地下水中移动扩散,对当地居民生活造成影响。(2)通过在研究区人口稠密与矿产资源丰富的乡镇地表水取样计523件,计算出地下水中氡浓度均值为18.54 kBq·m^(-3),范围为1.06~298.00 kBq·m^(-3)。研究区地下水中氡浓度差异较大,区内八尺、差干、仁居、泗水及中行镇的地下水中氡浓度均值较高,东石、河头、热柘、上举、石正镇的均值略低,但跃动范围大;大柘和长田镇的均值低且平稳。(3)研究区内地下水中氡所致居民年有效剂量均值偏高,已达剂量限值的10%,针对部分高氡浓度地下水的辐射危害,可以通过寻找新的水源替代现有地下水、寻找低氡水源措施;或面临水源解决困难必须使用高氡浓度地下水时,应避免在密闭环境中加热或使用地下水、避免直接食用生地下水,在有条件的情况下,可通过活性炭吸附、水中氡脱气装置等措施除去地下水中的氡。研究成果为加强当地辐射环境保护提供依据。

A uranium concentration area in northeast Guangdong is rich in mineral resources and is one of the important nuclear raw material bases in Guangdong Province.Based on the results of the survey on radon concentration in groundwater in the region,analyse the geological environment of different regions,types of water sources and other factors,explain the reasons for the differences in radon concentration in groundwater in the region,assess the impact of radon in groundwater in the region on the local radiation environment and residents,indicate the problems that should be paid attention to during the use of groundwater,and put forward measures and suggestions for strengthening radiation environmental protection.The results show that:(1)the enrichment of uranium ore in the study area will cause the local natural radioactive background to be high,and the waste rock,dust and waste water produced during uranium exploration and mining contain radionuclides such as^(238)U、^(232)Th and^(226)Ra,which may all cause radioactive pollution to the local area under the action of rainwater and runoff washing and infiltration,especially radon gas can move and diffuse in the crevices of rock and ore,surface soil and groundwater,affecting the life of local residents.(2)By taking 523 surface water samples from densely populated towns with rich mineral resources in the study area,the average radon concentration in groundwater was calculated to be 18.54 kBq·m^(-3)),with a range of 1.06 to 298.00 kBq·m^(-3)).The average radon concentration in groundwater in the study area varies greatly.The average radon concentration in groundwater in Bachi,Chagan,Renju,Sishui and Zhongxing townships in the area is higher,while the average values in Dongshi,Hetou,Jiezhe,Shangju and Shizheng townships are slightly lower,but with a wide range of jump;the average values in Dazhe and Changtian townships are low and stable.(3)The average annual effective dose due to radon in groundwater in the study area is high,reaching 10%of the dose limit.In view of the radiation hazards of some groundwater with high radon concentration,measures can be taken to replace existing groundwater by finding new water sources and finding low radon water sources;or when faced with difficulties in solving water sources and must use groundwater with high radon concentration,avoid heating or using groundwater in a closed environment,avoid direct consumption of raw groundwater and,if possible,remove radon from groundwater through measures such as activated carbon adsorption and radon degassing devices in water.The results of the study provide a basis for enhancing local radiation protection.